A new study at the University of Guelph and the University of Waterloo have found that the United States Department of Agriculture (USDA) recommended diet is too land-intensive for the planet. If everyone on the planet followed this recommended diet, then an additional gigahectare of land (the size of Canada) devoted agriculture would be needed to produce this food, exceeding the amount of fertile land actually available. This means that these dietary guidelines are fundamentally flawed and that not only nutrition, but also the long-term stability of the food system and of the environment need to be considered when creating them.

This study focuses specifically on the supply of food needed to feed the world based on USDA dietary recommendations, and the land required to achieve this supply, regardless of the accessibility of the food to the world population and how much of this food is lost or wasted from farm to table. Results show that in North America, land could be spared by switching to the USDA recommended diet, because the current consumption of land-intensive foods by people in this area, such as meat products, is higher than the USDA guidelines recommend. Conversely, Africa, Eastern Europe, the European Union and Oceania would cause a large land deficit by following the USDA recommended diet. Focusing in on the European Union, where instances of malnourishment are currently infrequent, causing a land deficit, suggests that the USDA guidelines are unsustainable when it comes to land-intensive foods.

The information in this study is novel in terms of the physical quantification of the land required to feed the world according to USDA guidelines, however, the results and implications line up with what the sustainable diets discourses have been saying for many years. As early as 1971, Frances Moore Lappé’s pioneering book, Diet for a Small Planet, pointed out the consequences of unfair and ineffective food policies that favor meat production over plant-based diets. Lappé advocated for change toward overall consumption of food that is lower down the food chain and placed urgency on the need of corporate and social responsibility to achieve this.

To feed a person on a plant-based vegan diet for one year, requires one-sixth of an acre of land. To feed a person on a vegetarian diet including egg and dairy products, requires three times that amount of land. The average American’s diet, that is high in meat, egg and dairy consumption, requires 18 times as much land. This accounts for the land required to grow the food needed to feed the livestock as well as the land needed to keep livestock. There are currently 9 billion livestock maintained on US soil to meet the demand of animal protein consumed by Americans. These livestock consume 7 times more grain than is consumed directly by the entire American population. This amount of grain would be sufficient to meet the needs of 840 million people on a plant-based diet. Additionally, producing 1 kg of animal protein requires 100 times more water than producing 1 kg of grain protein. This incorporates the water needed to grow the amount of feed needed to maintain the livestock over the course of their lives as well as to support the livestock themselves. For example, to produce 1 kg of beef requires about 13 kg of grain and 30 kg of hay. Approximately 17 000 L of water is needed to grow that grain and about 30 000 L for the hay.

Given the land and resource intensity of meat production, devoting more land to meat production to meet the USDA guidelines worldwide is neither a feasible nor sustainable way to feed to world. For food production to be sustainable, it must not compromise the ability of future generations to meet their own needs. Current food production is condoning the overuse of chemical fertilizers, land and water, degrading the soil, accelerating biodiversity loss, altering biochemical cycles, disturbing the carbon cycle and supports unfair trading practices. These exploitative and destructive patterns are severely compromising the health and even the existence of future generations as well as future planetary health.

Given this, it is no surprise that the policies surrounding food production and standardized dietary guidelines are in serious need of an overhaul, but this is not the first time researchers are saying this. In 1986 Joan Gussow and Kate Clancy coined the term “sustainable diet,” arguing that food choices cannot be solely based on nutrition, but must also incorporate environmental, cultural and economic and ethical criteria. A sustainable diet therefore works toward protecting and respecting biodiversity and natural ecosystems, is culturally acceptable, accessible, economically just and affordable, nutritionally sufficient, safe, and healthy.

Sustainable diets are therefore needed because as humans, our well-being is founded on the well-being of the environment in which we live. Anything threatening its well-being, integrity and stability is inherently threatening our own. This new research supports the urgency of policies that promote sustainable diets by putting a quantitative lens on this ethical foundation of sustainability and implies that dietary guidelines must consider sustainable global land use, equity, and natural ecosystem conservation in addition to human health requirements.